Method for the sequential production of a heterogeneous catalyst library

ABSTRACT

The sequential production of a library of N different solids, in particular heterogeneous catalysts, where N within a day is an integer of at least 2, is performed by
         a) producing at least two different sprayable solutions, emulsions and/or dispersions of elements and/or element compounds of the chemical elements present in the catalyst and optionally of dispersions of inorganic support materials,   b) continuously metering the at least two different solutions, emulsions and/or dispersions in a predefined ratio into a mixing apparatus in which the solutions, emulsions and/or dispersions are homogeneously mixed,   c) continuously drying the mixture removed from the mixing apparatus and recovering the dried mixture,   d) changing the ratios in step b) and repeating steps b), c) and d) (N−1) times until N different dried mixtures are obtained,   e) optionally shaping and optionally calcining the mixtures to give the solids.

The invention relates to a process for producing a heterogeneouscatalyst library and to an apparatus suitable therefor.

To prepare and study novel chemical compounds, in addition to classicchemistry which is directed toward the synthesis and study of individualsubstances, which combinatorial chemistry has developed. In thisapproach, a multiplicity of reactants were reacted in a one-potsynthesis and analyzed as to whether the resultant reaction mixturedisplayed the desired properties, for example a pharmacologicalactivity. If an activity was found for such a reaction mixture, it wasnecessary to determine in a further step which specific substance in thereaction mixture was responsible for the activity. In addition to thehigh expenditure for determining the actual active compound, it wasdifficult with a multiplicity of reactants to exclude unwanted sidereactions.

In another high-throughput synthesis approach, a multiplicity ofcompounds are synthesized by specific dosage and reaction of a number ofreactants in a multiplicity of different reaction vessels. In thisprocess, preferably, in each reaction vessel one reaction product ispresent, so that in the event of, for example, a given pharmacologicalactivity of a mixture, the starting materials used for its preparationare known immediately.

In addition to the first applications of this more specificcombinatorial synthesis in the search for novel pharmacologically activesubstances, very recently the synthesis method has also been extended tolow-molecular-weight organic compounds and to organic and inorganiccatalysts.

X.-D. Xiang et al., “A Combinatorial Approach for Materials Discovery”,Science 268, (1995), pages 1738 to 1740 describe the preparation ofBiSrCaCuO and YBaCuO superconductivity films on substrates, acombinatorial array of different metal compositions being obtained byphysical masking processes and vapor deposition techniques in thedeposition of the appropriate metals. After the calcination, differentcompositions are present at different positions of the array and can bestudied by microprobes, for their conductivity for example.

WO 96/11878 describes, in addition to the preparation of suchsuperconductivity arrays, the preparation of zeolites, the amountsrequired in each case being metered without prior mixing from aplurality of metal salt solutions using an ink jet onto a type of spotplate, a precipitation starting on addition of the last solution. BSCCOsuperconductors can also be prepared by separate metering of theindividual nitrate solutions of the metals required by spraying onto atype of spot plate and subsequent heating.

WO 98/47613 discloses a number of processes by which libraries ofpotentially interesting materials can be produced using sputtering, CVDor PVD techniques. In the core, this application relates to the use ofsuitable masking techniques which makes possible defined separation ofat least two components (which are present as separate substrates) onone substrate, as a result of which composite materials are obtained.Furthermore, by means of the process, complete libraries of materials ofdiffering composition can be produced by producing gradients on thesputtered substrate.

The processes described have a number of disadvantages. Firstly,continuous compact libraries are produced on one substrate which canonly be tested separately from one another for desired propertiessubsequently by mechanical separation. Secondly, the sample amountsproduced by these substrate coating techniques are very small (only afew milligrams as thin layers on substrates), so that a definedtreatment, such as by sintering processes or treatment with definedmedia (liquids, gases), poses difficulties, in particular in the case ofreproducing process parameters or scaling up sample quantities. Afurther disadvantage of the sputtering process is that the morphology ofthe materials produced can differ greatly with respect to crystallinityand particle size from materials produced by conventional techniques,that is to say by spraying, precipitation or impregnation techniques.Thus applicability of the parameters determined by this combinatorialmethod is uncertain, because material properties, for example hardness,ionic conductivity, heat conductivity, dielectric constants, electricalconductivity, thermoelectromotive force, magnetic properties, porosity,depend to a great extent on, inter alia, the crystallinity, thecrystallographic nature of the crystallites or the degree of fineness ofthe particles, the defects and grain boundaries and other parameterswhich can be greatly affected by the production parameters. A furtherproblem of the production techniques described is testing a usefulproperty of the material without the effect of the substrate, which isonly possible with difficulty owing to the small amount of material andfilm thickness. For special applications, such as electronic or magneticproperties, it is of great interest to produce unsupported materials andtest the resultant materials for their useful properties.

DE-A-199 55 789 discloses a process for the combinatorial production ofa library of materials in the form of a two-dimensional matrix in thesurface region of a flat substrate in which at least two differentsprayable material components, for example solutions or dispersions, aresprayed onto the same side of the substrate from at least two spraynozzles which are at a distance from the substrate and from one another,so that materials of a different composition are obtained in differentsurface regions of the substrate.

This process also does not permit the production of relatively largeamounts of material.

DE A-103 03 526, which has an earlier priority (priority of Jan. 29,2003) but which had not been published at the time of filing the presentapplication, relates to a process for producing a multi-metal oxidecomposition, in which, from the starting compounds required forproducing the multi-metal oxide composition, a mixture solution isproduced continuously in a solvent, the mixture solution is continuouslyfed into a drying apparatus to remove the solvent and the resultantsolid is thermally treated at elevated temperature. In this process theprecursor solutions are made up of at least two spatially separatedsubsolutions, each containing subquantities of the required startingcompounds.

WO 02/04112 relates to processes for analyzing heterogeneous catalystsin a multi-variable screening reactor. The reactor is preferably aparallel flow reactor. FIG. 2A shows a parallel flow reactor in whichdifferent reaction conditions can be set in different flow reactors.Different evaluation methods can be carried out.

EP-A-1 283 073 describes the parallel production of supported catalystsin impregnation vessels in which supports are impregnated in paralleland are then dried and calcined.

It is an object of the present invention to provide a process forproducing a library of solids, in particular heterogeneous catalysts,which avoids the disadvantages of the known processes and also permitsthe preparation of relatively large amounts of heterogeneous catalystsin a rapid and efficient manner.

We have found that this object is achieved according to the invention bya process for the sequential production of a library of N differentsolids, in particular heterogeneous catalysts, where N is an integer ofat least 2, by

-   -   a) producing at least two different sprayable solutions,        emulsions and/or dispersions of elements and/or element        compounds of the chemical elements present in the catalyst and        optionally of dispersions of inorganic support materials,    -   b) continuously metering the at least two different solutions,        emulsions and/or dispersions in a predefined ratio into a mixing        apparatus in which the solutions, emulsions and/or dispersions        are homogeneously mixed,    -   c) continuously drying the mixture removed from the mixing        apparatus and recovering the dried mixture,    -   d) changing the ratios in step b) and repeating steps b), c)        and d) (N−1) times until N different dried mixtures are        obtained,    -   e) optionally calcining the mixtures to give the solids, in        particular heterogeneous catalysts.

The term “library of heterogeneous catalysts” can mean here that amultiplicity of different heterogeneous catalysts is produced on onesubstrate, the substrate having subdivisions for the separate uptake ofthe separate heterogeneous catalysts. Preferably, in this case, theabovementioned numbers of different heterogeneous catalysts are presenton the substrate.

Alternatively, the different solids, in particular heterogeneouscatalysts, can be introduced into a multiple reactor in which they thenform an array or a library of heterogeneous catalysts. The multiplereactors can be, for example, tubular reactors, which contain amultiplicity of tubes, in particular 2, 4, 8, 16 or 64, etc. tubes.Suitable multiple reactors are described, for example, in WO 02/04112,DE-A-199 55 789, DE-A-199 59 973 and the literature cited therein.

We have found that this object is achieved according to the invention,in addition, by a process for the parallel testing of the libraries ofsolids obtained by the abovementioned process, which solids are inparticular heterogeneous catalysts, for a desired catalytic property,comprising separately introducing the individual solids into multiplereactors and subsequently carrying out the steps required for testingfor a desired catalytic property. The processes for the parallel testingare likewise described in more detail in the publications above.

A multiplicity of organic or inorganic solids can be produced accordingto the invention. In particular, inorganic solids, especiallyheterogeneous catalysts, are produced. N different solids are producedwithin one day (24 hours). The inventive process permits the rapidsequential production of N different solids, in particular heterogeneouscatalysts, within a short time. By conventional processes, to date, onlyone solid or heterogeneous catalyst could be produced within one day.The inventive process also permits the automation and the considerableacceleration of the production of solids, in particular heterogeneouscatalysts.

In step b) homogeneous mixing is carried out. Homogeneous mixing isdemonstrated after drying the mixture by analyzing the compositions ofthe dried particles or grains. According to the invention, betweenindividual dried grains there is a difference in composition of at most30%, preferably at most 15%, in particular at most 5%. Differences incomposition here can be measured by a spatially resolved microstructuralelemental analysis, for example by ESCA, EDX, XPS and similar methods.

The shaping in step e) includes, for example, tabletting or producingfragments. For example, the dried mixtures can first be tableted,whereupon the tablets are crushed to form fragments, which is followedby calcination.

N is an integer of at least 2, preferably at least 9, particularlypreferably at least 45, in particular at least 90. This means that inthe process at least 2, preferably at least 9, particularly preferablyat least 45, in particular at least 90, different heterogeneouscatalysts are produced one after the other. The upper limit can be, forexample, 50 000, preferably, for example, 5 000. This is changed bychanging the ratio of the different solutions, emulsions and/ordispersions of elements and/or element compounds of the chemicalelements present in the catalyst. The solutions, emulsions and/ordispersions are customarily continuously metered by pumps. Customarily,for each solution, emulsion and/or dispersion there is provided astorage vessel which contains the respective solution, emulsion and/ordispersion. Each of the storage vessels preferably has a volume of from50 to 50 000 ml, more preferably from 100 to 10 000 ml, particularlypreferably from 500 to 5 000 ml. Each of the storage vessels isconnected to the mixing apparatus by means of a pump via a pipe or atube, so that from each storage vessel one liquid stream canindividually be pumped into the mixing apparatus. In the mixingapparatus the different substreams of the individual storage vessels arethereby combined to form a total stream. The different substreams flowtogether to form the total stream each at a predetermined flow velocity.The metering of the different streams into the mixing apparatus can beperformed directly within the mixing apparatus or upstream of the mixingapparatus. The mixing apparatus can be any suitable mixing apparatuswhich is suitable for mixing as homogeneously as possible solutions,emulsions and/or dispersions. For example, it can be a static or dynamicmixer. Preferably, a dynamic mixer is used. The mixing action should beof a size such that a system as homogeneous as possible, as described,is produced, for example in the form of a solution, emulsion and/ordispersion.

In the simplest case, the at least two solution substreams are thenpassed to the two inlets of a T piece (preferably the feeds narrow inthe inlet part of the T piece). In the interior of the T piece the twosolution substreams combine and flow together as a total solution streaminto the outlet part of the T piece via which the total solution streamis removed from the T piece. After the two solution substreams combine,on their further passage as total solution stream, their essentiallyhomogeneous mixing takes place, which can be caused, for example,predominantly by turbulence generated during their combination.

In the outlet path, however, a static mixer (for example one of the SMXStype from Sulzer Chemtech, D-61239 Ober-Mörlen-Ziegenberg) and/or adynamic mixer can additionally be integrated, through which the totalsolution stream flows and leaves as an essentially homogeneous mixedsolution stream. In principle, static or dynamic mixers are spaces whichcontain fixed obstacles or moving obstacles, respectively, which act onthe flow of the mixed solution stream so that in the same turbulence isproduced which causes the mixing to form a mixed solution stream.“Static mixer” means a mixer which contains fixed mixing devices, forexample flow pins, which the materials to be mixed flow past and aremixed together by vortexing and other disturbances; “dynamic mixers” arethose which contain active mixing devices, for example in the form ofrotating mixing veins; in these the materials to be mixed are mixedtogether by active transport.

It has been proven in practice to give additional reinforcement to themixing in the mixing zone, or to cause it exclusively, by the action ofultrasound (for example ultrasonic transducer UIP 50 from Dr.Hielscher). For this, for example, a rod-shaped ultrasonic probe can beintroduced into the mixing zone.

Of course, the number of inlets of the “T piece” in the abovementionedexemplary embodiment of the inventive process can also be more than two,without significant change in the basic principle of the procedure.

The mixture is transferred from the mixing apparatus into a dryer, whichpermits rapid drying of the solutions, emulsions and/or dispersions. Themixture can be passed from the mixing apparatus to the dryer through afurther pipe having an intermediate pump. It is also possible to utilizethe preexisting pressure, or the preexisting flow, for the transportinto the dryer.

The mixture is also sometimes drawn through the dryer by suction, in theevent of suitable geometry.

The individual substreams can, as described, first be mixed in a mixingapparatus and then transferred to the dryer. It is also possible tocombine the individual components directly in a spray nozzle of thedryer, so that mixing and start of drying coincide.

The dryers used can be all suitable dryers using which rapid drying ofsolutions, emulsions and/or dispersions is possible. Preferably, spraydryers or spray freeze dryers are used. The spray dryers or spray freezedryers can be designed in a conventional manner.

The mixed solution stream produced as described can be passed directlyand along the shortest route to the atomizer head of a spray dryer (forexample a Minor Hi-Tec Niro Atomizer from Niro, Copenhagen, DK) anddisintegrated into finely divided droplets which are dried by contactwith hot gas (for example air or nitrogen or mixtures of air andnitrogen, or noble gases, or carbon oxides). The inlet temperature ofthe hot gas, in the case of the abovementioned spray dryer, can be inthe inventive process, for example, from 200 to 400° C., preferably from310 to 330° C. The outlet temperature of the dry gas should be accordingto the invention from 100 to 200° C., preferably from 105 to 115° C. Inthe spray dryer, the atomized mixed solution and the hot dry gas can beconducted co-currently or counter-currently. The droplet sizes resultingon atomization is customarily from 5 to 1 000 μm, frequently from 10 to100 μm. The drying time of such droplets is, in conventional spraydryers, less than one second. In principle, the spray drying in theinventive process can also be carried out as described in EP-A-0 603836.

The total solution can be atomized in the inventive process by means ofnozzles (for example by means of swell-plate nozzles and two-fluidnozzles), by means of gas-pressure atomizers or by means of sprayingdisks or spraying baskets (sometimes also termed “rotary nozzles”).Two-fluid nozzles, spraying disks and spraying baskets are preferredaccording to the invention. Although the latter, compared with othernozzles, require greater technical expenditure with higher energyconsumption, they are less sensitive to solid particles which may form.The total solution in general then flows unpressurized to the disk orbasket center, is distributed and is sprayed off as a hollow cone fromthe smooth disk rim or from the perforated basket rim.

The solution substreams in the inventive process, however, can also befed directly to a dynamic mixer, as described by DE-A-100 43 489,micromixers according to DE-A-100 41 823 or mixer nozzles according toDE-A-199 58 355 and mixed according to the invention in these. Mixingnozzles of this type which can be used for the inventive process aresmooth-jet nozzles, levo nozzles, Bosch nozzles or jet dispersers.Preference is given according to the invention to the use of mixernozzles which cause not only the combination of the solution substreamsand their mixing, but also the division of the resultant mixed stream.The atomized total solutions can then be dried, as in a spray dryer, bymeans of hot gases co-currently or counter-currently. The advantage ofthe inventive procedure is based on the production of stablesubsolutions which are not combined and mixed continuously until theyare flowing, as a result of which a mixed solution stream is produceddirectly and with minimal time demand, which mixed solution streams canbe spray dried with a narrow residence time distribution without loss oftime.

The ratio in the above steps b) and d) can be set and changed bychanging or adapting the flow velocity in the different solutions,emulsions and/or dispersions during metering into the mixing apparatus.Differing types or concentrations of starting materials can be presentin the different storage vessels. To avoid excessive amounts of liquid,depending on the desired product composition, different concentrationsof the solutions, emulsions and/or dispersions can also thus be takenoff from the storage vessels. The total amount, that is to say the totalstream, can be varied, for example within the range of the optimum modeof action of the drying apparatus, in particular the spray dryer. Thetotal stream is thus controlled in such a manner that optimum drying isensured in the subsequent step. The optimum working ranges of, forexample, spray dryers are known to those skilled in the art. The mixedsolutions, emulsions and/or dispersions can also be diluted by water toachieve a desired amount of liquid and a desired product content.Preferably, the total stream which is produced from combining thedifferent substreams from the different storage vessels is keptessentially or exactly constant. This means that a constant materialstream (total stream) flows through the mixing apparatus and the dryer.This has the advantage that the control of the mixing action and thedrying action does not have to be renewed for each different catalystcomposition, but is set once and then remains constant in the process.Deviations of a maximum of ±50%, preferably a maximum of ±20%, inparticular a maximum of ±5%, can frequently be tolerated. In theinventive process, the substreams from the different storage vessels arefirst set to obtain a desired mixing ratio of the components. Then,spray drying is continued with these substreams until a desired amountof heterogeneous catalyst or precursor thereof is obtained. Preferably,the different heterogeneous catalysts are each produced in amounts offrom 0.1 to 500 g, preferably from 1 to 100 g, in particular from 5 to50 g. It is also possible to produce larger and smaller amountsaccording to the invention.

After the desired amount of the catalyst or catalyst precursor has beenproduced, the substreams are changed to achieve a new catalystcomposition. Then mixing and drying are performed again until thedesired amount of catalyst has been produced. For each further catalystcomposition, the steps are repeated one after the other (sequentially).

To achieve an as accurate as possible batch composition of the differentheterogeneous catalysts, it is also possible to clean the system in aconventional manner between the two catalyst production operations. Inthis case, after producing the heterogeneous catalysts the substreamsare turned off and the entire apparatus is cleaned, for example bywashing with deionized water, the pH of which can be basic, neutral oracidic by adding acids and alkalis. The substreams for the next catalystcomposition are then turned on and the catalyst production is continued.

The design of the size of the process can be matched to the respectiverequirements. Preferably, a total stream in the range from 600 ml/h to15 l/h, particularly preferably from 0.5 to 3 l/h, in particular from1.4 to 2.6 l/h, is employed. This total stream of the individualsolutions, emulsions and/or dispersions is preferably kept as constantas possible during metering into the mixing apparatus and for drying, inorder to ensure constant process conditions.

Operation should be carried out in a range for the good operation of aspray dryer.

With preference, the time period between mixing the solutions, emulsionsand/or dispersions and drying should be kept as small as possible. Withpreference the time period is less than 10 minutes, preferably less than5 minutes, more preferably less than 1 minute, particularly preferablyless than 10 seconds, in particular less than 3 seconds, especially lessthan 1 second. The time period can be met by means of the equipmentdesign of the connection between mixing apparatus and dryer, and alsovia the flow velocity. Preference is given to short paths between mixingapparatus and dryer. The mixing can also take place at the dryer inlet.

With preference, the ratio in step b) set and changed by centralcomputer is control of the output of pumps each of which convey thedifferent solutions, emulsions and/or dispersions separately into themixing apparatus. Via the computer, not only the individual pump outputcan be controlled, but also the conveying period can be predetermined.The total process for the sequential production of a heterogeneouscatalyst library can be carried out under computer control. Via asuitable software program and suitable computer control of the pumps,before the process is carried out the desired catalyst compositions canbe determined and input into the computer. After charging the storagevessels with the desired solutions, emulsions and/or dispersions, thecomputer can then automatically calculate and control the output ratesand amounts of the individual pumps. At the end of the production of acatalyst of a desired composition, the production apparatus can becleaned under computer control, whereupon production of the nextcatalyst composition follows.

The computer can be provided with suitable input and output media orapparatuses. Customarily the computer has a screen and a keyboard andalso a printer.

Also, according to the invention, not only the mixing in the mixingapparatus but also the drying in the dryer can be computer controlled.For example, a temperature program for the spray drying can be provided.

The solids obtained after the spray drying, for example homogeneous orheterogeneous catalysts, in particular heterogeneous catalysts, can becollected, stored and further processed in a suitable manner.Customarily the individual heterogeneous catalysts are collected inseparate vessels and stored for further use. The type of collection andstorage depends here on the further use. For example, the heterogeneouscatalysts obtained can be introduced into different tubes of a tubularreactor or into different boreholes of a body made of a solid material.A corresponding reactor design which is suitable, in particular, forcarrying out heterogeneously catalyzed gas-phase reactions is describedby way of example in DE-A 199 55 789.

The heterogeneous catalyst produced by the inventive process can also bearranged in an array of vessels, in which case the arrangement of thevessels in the array can likewise be performed under computer control.By this means it is possible to store in the computer and keep availablethe individual composition of a heterogeneous catalyst batch in oneposition of the array.

The mixtures can be calcined to give the heterogeneous catalysts in stepe) separately for the individual catalyst mixtures or together in thedescribed array. By this means it can be assured that constantcalcination conditions are maintained for all catalyst mixtures.

The catalyst precursor compositions are thermally treated attemperatures in the range from 250 to 1500° C., for example from 300 to1000° C. (materials temperature), for example in a gas atmospherecontaining inert or reactive gases (that is to say usually a gasatmosphere partially having O₂ and/or NH₃ in certain calcinationphases). In addition, the calcination atmosphere can also contain CO₂,steam, acrylonitrile, NOx.

Reactive gases can have either reducing or oxidizing action. Thecalcination time is generally from a few minutes to several hours,customarily from 0.5 to 3 hours.

In the inventive process, N different mixtures are produced in themixing apparatus and dried in the dryer.

According to the invention, any suitable solutions, emulsions and/ordispersions of elements and/or element compounds of the chemicalelements present in the heterogeneous catalyst can be used. Preferably,the sprayable solutions, emulsions and/or dispersions comprise elementsof groups I B, II B, III B, IV B, V B, VI B, VII B and VIII, thelanthanides, actinides or groups I A, II A, III A, IV A, V A, VI A andVII A of the Periodic Table of the Elements or their compounds ormixtures thereof. Components which are sprayed in the process arepreferably metal salt solutions or metal salt dispersions orcorresponding oxides. Optionally, dispersions of inorganic supportmaterials such as Al₂O₃, ZrO₂, SiO₂, Y₂O₃, TiO₂, activated carbon, MgO,SiC or Si₃N₄ can also be used, provided that they are of a particle sizewhich permits spray drying.

According to one embodiment of the invention, the process does not servefor producing a multi-metal oxide composition M of the generalstoichiometry IMo₁V_(a)M¹ _(b)M² _(c)M³ _(d)M⁴ _(e)O_(n)  (I),

where

-   -   M¹=at least one of the elements of the group consisting of Te        and Sb;    -   M²=at least one of the elements of the group consisting of Nb,        Ti W, Ta, Bi, Zr and Re;    -   M³=at least one of the elements of the group consisting of Pb,        Ni, Co, Fe, Pd, Ag, Pt, Cu, Au, Ga, Zn, Sn, In, Ce, Ir, Sm, Sc,        Y, Pr, Nd and Th;    -   M⁴=at least one of the elements of the group consisting of Li,        Na, K, Rb, Cs, Ca, Sr, Ba;    -   a=from 0.01 to 1,    -   b=from ≧0 to 1,    -   c=from >0 to 1,    -   d=from ≧0 to 0.5,    -   e=from ≧0 to 1 and    -   n=a number which is determined by the valence and frequency of        the elements in (I) different from oxygen.

The liquid mixtures generally comprise a liquid chemical component whichis used as solvent, emulsifier of dispersion aid for the furthercomponents of the mixture. Solvents or dispersion aids used are organicsolvents, emulsifying aids and/or water, preferably water. Examples ofsuitable organic solvents are alcohols and paraffins and also acids suchas acetic acid or inorganic acids, esters, ethers, ketones. In addition,mixtures of solvents with suitable dispersants such as organic additivescan be used. If dispersions/suspensions are sprayed, the particles whichare present in the dispersion/suspension should preferably be <50 μm,particularly preferably <10 μm. It is also possible according to theinvention to convert finely particulate powders into stable dispersionsor suspensions. In order to have to evaporate as little as possibledispersant, volume fractions as high as possible of the solids withsimultaneously low viscosity of the dispersions or suspensions to besprayed should be used. Content by mass of preferably from 0.5 to 50% byweight, particularly preferably from 1 to 30% by weight, are obtainedwhen suitable dispersants are used.

Suitable dispersants are described, for example, in DE-A 199 55 789. Thespecific dispersants specified there can be used for dispersing amultiplicity of different finely particulate solids in a flowable medium(dispersion medium). Preferably from 0.1 to 10% by weight, particularlypreferably from 0.5 to 5% by weight, of the dispersion media are used,based on the solid.

Preferred starting materials for producing the inventive heterogeneouscatalysts are, for example, ammonium compounds. The solutions, emulsionsand/or dispersions have a dissolved content or solids content ofpreferably from 0.5 to 50% by weight, particularly preferably from 1 to30% by weight, based on the total solution, emulsion and/or dispersion.Starting compounds for the selected chemical elements which come intoconsideration are in principle the elements themselves, preferably infinely divided form, furthermore all compounds which contain theselected chemical elements in a suitable manner, such as oxides,hydroxides, oxyhydroxides, inorganic salts, preferably nitrates,carbonates, acetates and oxalates, organometallic compounds, alkoxidesetc. The respective starting compounds can be used in the form ofsolutions, emulsions and/or dispersions.

Metals can be added in the form of their nitrates, oxalates, carbonates,hydrogen carbonates, chlorides, chlorates, sulfates, oxysulfates,hydrogen sulfates, hydroxides, as oxides, as peroxides, as carboxylates,for example acetates, oxalates, citrates or tartrates, or else asalkoxides. Some examples of these are:

A. Ammonium Salts

Ammonium heptamolybdate

Ammonium metavanadate

Ammonium paratungstate

B. Nitrates

Iron nitrate (II or III)

Silver nitrate

Bismuth nitrate

C. Sulfate/Oxysulfate

Iron sulfate

Titanium oxysulfate

D. Oxalate:

Niobium oxalate

E. Tartrates

Antimony tartrate

Niobium tartrate

In addition, it is possible to add separately solutions of ammoniumacetate, acetic acid, ammonium oxalate, oxalic acid, ammonium tartrate,tartaric acid, ammonium citrate, citric acid or else ammonium EDTA, andalso mixtures of these components can be added.

In addition, buffer systems can be charged, added and co-sprayed both tothe individual salts and as a separate buffer solutions, for example thecarbonate buffer system, the borate buffer system, the acetate buffersystem or else the citrate buffer system.

Preferred element compounds, in particular of catalytically activemetals, are water-soluble oxides, hydroxides, acids or salts of organicor inorganic acids, neutralized with inorganic or organic bases. Activemetals are preferably found in the subgroups of the Periodic Table ofthe Elements for example in subgroup V and subgroup VI for oxidationcatalysts and in the platinum group for hydrogenation catalysts. Theinventive process also permits screening of (atypical) elements whichhave not to date been considered as catalytically active, in particularmetals and metal oxides. Preferably there are contained in theindividual solutions, emulsions and/or dispersions in each case one ormore, more preferably 2 or more, particularly preferably 3 or more,chemical elements, but generally no more than 50 different chemicalelements at an amount in each case of more than 1% by weight.Preferably, the chemical elements are present in the mixtures in a veryintimate mixture, for example in the form of a mixture of variousmiscible solutions, intimate emulsions of a small droplet size and/orpreferably as a suspension (dispersion) which contains the relevantchemical elements generally in the form of a finely divided precipitate,for example in the form of a chemical mixed precipitate. The use ofbrines and gels is also proven, in particular of those which contain therelevant chemical elements in a substantially homogeneous distribution.

The inventively produced heterogeneous catalysts can be suitable for anychemical reactions. Preferably homogeneous catalysts are for reactinggases or gas mixtures, in particular oxidation reactions. Examples ofsuitable reactions are the destruction of nitrogen oxides, ammoniasynthesis, ammonia oxidation, oxidation of hydrogen sulfide to sulfur,oxidation of sulfur dioxide, direct synthesis of methylchlorosilanes,oil refining, oxidative coupling of methane, methanol synthesis,hydrogenation of carbon monoxide and carbon dioxide, conversion ofmethanol to hydrocarbons, catalytic reforming, catalytic cracking andhydrocracking, coal gasification and liquefaction, fuel cells,heterogeneous photocatalysis, synthesis of MTBE and TAME,isomerizations, alkylations, aromatizations, dehydrogenations,hydrogenations, hydroformylations, selective or partial oxidations (forpreparing saturated or unsaturated carboxylic acids, for example propeneto acrylic acid, propane to acrylic acid, butane to maleic anhydride),ammoxidations (for example propane to acrylonitrile), preparation ofsaturated or unsaturated carboxylic acids, anhydrides and aldehydes,ketenes, aminations, halogenations, nucleophilic aromatic substitutions,addition and elimination reactions, oligomerizations and metathesis,polymerizations, enantioselective catalysis and biocatalytic reactions.

The inventively used solutions, emulsions and/or dispersions can inaddition be adjusted to a defined pH range by adding acids and/or bases.It is also possible to meter acids and/or bases from separate storagevessels into the mixing apparatus.

In many cases, pH-neutral suspensions are used.

The invention also relates to an apparatus for the sequential productionof a library of N different heterogeneous catalysts, where N is aninteger of at least 2, comprising a number of at least 2 storage vesselsfor receiving solutions, emulsions or dispersions of elements and/orelement compounds of the chemical elements present in the catalyst andoptionally of dispersions of inorganic support materials,

a mixing apparatus for mixing the solutions, emulsions and/ordispersions,

pumps and pipe connections for the individually independent connectionof the storage vessels to the mixing apparatus,

an apparatus for drying the mixture passed out of the mixing apparatuswhich is connected to the mixing apparatus via piping, and

a computer which controls the output rate of the pumps.

The apparatus for drying is preferably a spray dryer or spray-freezedryer. Customarily two or more storage vessels are used. Preferably,from 2 to 20 storage vessels, particularly preferably from 3 to 8storage vessels, are used. The dimensioning of the storage vessels hasalready been described above. The inventively used apparatus in additionpreferably has the abovedescribed features and properties.

The inventive process and the inventive apparatus permit in advantageousmanner the production of larger amounts of catalyst than is possible bythe known combinatorial processes. By means of the automated production,numerous catalyst compositions can be synthesized in a short time andwith low expenditure. The catalysts can be obtained in a form in whichthey are also used in a later practical application. The inventivecatalyst production is thus considerably closer to practice than thepreviously known processes.

The invention will be described in more detail by the examples below.

EXAMPLE 1

Production of a Multi-Metal Oxide Composition

To produce a subsolution A, first 4 000 ml of water were heated to 80°C. in a glass vessel. Therein, maintaining 80° C. and with stirring,706.2 g of ammonium heptamolybdate from H. C. Starck, Goslar (DE) havingan MoO₃ content of 81.53% by weight (=4 mol of Mo) were dissolved.Likewise at 80° C., 141.0 g of ammonium metavanadate from H. C. Starck,Goslar (DE) having a V₂O₅ content of 77.4% by weight (=1.2 mol of V)were stirred into the resultant clear solution and dissolved. Likewiseat 80° C., 211.28 g of Te(OH)₆ from Fluka Chemie GmbH, Buchs (CH) havinga Te(OH)₆ content of ≧99% (=0.92 mol of Te) were stirred into theresultant clear solution and dissolved. The resultant reddish solutionwas cooled to 25° C. and, with stirring, was supplemented with water oftemperature 25° C. to give a clear transparent subsolution A of a totalvolume of 4 500 ml.

To produce a subsolution B, 221.28 g of niobium ammonium oxalate from H.C. Starck, Goslar (DE) having an Nb content of 20.1% by weight (0.48 molof Nb) were dissolved in 1 000 ml of water which had been heated to atemperature of 80° C. The resultant clear transparent solution wascooled to 25° C. was supplemented with water which likewise had atemperature of 25° C. to give a clear transparent subsolution B having atotal volume of 1 500 ml.

The two stable aqueous solutions A and B were continuously pumped bymeans of two laboratory metering pumps of the type ProMinent, and oftype gamma g/4a, via two separate plastic tubes into the two inlet partsof a Y-shaped plastic T piece. The three tubular parts of the T piece (2inlet parts and 1 outlet part) each had an internal diameter of 5 mm anda length of 38 mm. The solution A was transported as a stream of avolumetric flow rate of 1 500 ml/h and the solution B as a stream of avolumetric flow rate of 500 ml/h. In the interior of the T piece, thetwo solution streams A and B were combined to form a total solutionstream of 2 000 ml/h which flowed into the outlet part of the T piece.In this was situated a type SMXS static mixer from Sulzer Chemtech,Ober-Mörlen-Ziegenberg (DE). The diameter of the static mixer was 4.8mm, and the length of the mixer bar was 35 mm. The end of the outletpart of the T piece was connected directly to the atomizer head of aspray dryer (Niro Atomizer, Minor-Hi-Tec type, from Niro, Copenhagen,(DK)) which atomized the fed mixed solution stream (droplet sizeapproximately 30 μm). Within the atomizer head which was mounted in thecenter of the hot-air distributor fixed to the ceiling of the dryingtower, the mixed solution steam flowed through a 15 cm long connectionline having an internal diameter of 6 mm directly to an atomizer disk(channel disk) rotating at 30 000 rpm. The resultant sprayed mist wasdried by a hot air stream (cocurrent, inlet temperature 320° C., outlettemperature 105° C.). Within 3 h, the 6 000 ml in total of totalsolution stream could be spray dried.

From the total solution stream of 2 000 ml/h, the internal diameter ofthe outlet part of the T piece and the length of the static mixingsection of 35 mm, a time period t¹ of approximately 1.2 seconds may becalculated, within which the combined subsolution streams A and B areconverted into an essentially homogeneous mixed solution stream.Additionally taking into account the transport of the mixed solutionstream from the outlet of the static mixer through the 15 cm longconnection line in the atomizer head having an internal diameter of 6 mmto the point of atomization, this gives a time period t² from combiningthe solution streams A and B to atomizing their mixed solution stream ofless than nine seconds. Incorporating a drying time of less than onesecond, the time period t³ from combination up to the dry powder is lessthan ten seconds. In accordance with the weighed stoichiometry ofsolution A and solution B and of the subsolution streams chosen (3:1),the resultant spray powder contains the elements Mo, V, Nb and Te in themolar stoichiometric ratio of Mo₁V_(0.3)Nb_(0.12)Te_(0.23) (if theoutlet part of the T piece was not connected directly to the atomizerhead of the spray dryer, but instead a 15 cm long transparent plastictube having an internal diameter of 6 mm was connected to the end of theoutlet part of the T piece, through which the mixed solution stream wastransported into a collection vessel situated beneath, a visualinspection found that the mixed solution stream contains no precipitatenot only on the entire length of the plastic tubing but also on itsarrival in the collection vessel and was clear and transparent on thecomplete extent; a filtration experiment on the mixed solution flowingout from the plastic tubing confirmed the freedom from solids).

150 g of the resultant spray powder were heated in a rotary sphere ovenaccording to FIG. 1 of DE-A 101 18 814 under air (10 l (S.T.P.)/h) at aheating rate of 5° C./min from room temperature (25° C.) to 275° C.Immediately thereafter heating was performed under a molecular nitrogenstream (10 l (S.T.P.)/h) at a heating rate of 2° C./min from 275° C. to650° C. and this temperature was kept for 6 h, maintaining the nitrogenstream. Then, maintaining the nitrogen stream, cooling was performed bythis itself, to 25° C. A black calcined multi-metal oxide activecomposition M was obtained.

By varying the substreams, different compositions of the multi-metaloxide composition could be obtained.

EXAMPLE 2

Nine catalysts were produced for the single-stage propane oxidation in apreparation system consisting in detail of 5 reservoir vessels,peristaltic pumps, mixer and spraying tower and in a central controlunit.

In heatable glass vessels (=reservoir vessels) each having a volume of 5l and which were equipped with KPG agitators, solutions of the followingcomponents were made up:

-   -   (i) 130 g/l of ammonium heptamolybdate (H. C. Starck, Goslar,        82.55% by weight of MoO₃) in deionized water (solution A),    -   (ii) 28 g/l of ammonium metavanadate (G.f.E., Nuremberg, 77.5%        by weight of V₂O₅) in deionized water (solution B),    -   (iii) 37 g/l of telluric acid (Fluka, 99% H₆TeO₆) in deionized        water (solution C) and    -   (iv) 200 g/l of ammonium niobium oxalate (H. C. Starck, Goslar,        22.0% by weight of Nb) in deionized water (solution D).

Each vessel is connected via a line (internal diameter 6 mm) to a mixingstar to which the individual solutions were led together. From there themixture of the dissolved metal salts passes through a mixer (ultrasonicemitter from Dr Hielscher, type UIP 50) and is then passed to a sprayingtower. The individual solutions were conveyed by 5 peristaltic pumps (1pump per reservoir vessel) to the mixing star and further into themixing vessel of the uyltrasonic emitter. The mixed solution was fed viaan overflow apparatus to the spraying tower which draws in thesolutions, in addition to the transport due to the pumps. The sprayingtower used (BASF in-house construction, diameter of the spraying tower35 cm) is equipped with a two-fluid nozzle and is charged with nitrogennot only for atomizing the aqueous mixture but also for drying thesprayed mixture particles (gas inlet temperature: 290° C.; gas outlettemperature 130° C.). The dried product is separated off in a cycloneand collected. The transport rates of the solutions A to D through theperistaltic pumps and the operation of the spraying tower are controlledby a central PC into which only the concentrations of the startingsolutions and the desired stoichiometry need to be input. When the spraydrying for a selected composition is complete, the collection vesselbeneath the cyclone must be exchanged, which can be performed manuallyor automatically.

The product obtained was tableted (diameter 16 mm, height=10 mm) andpreliminarily fragmented in a mortar (grain size fraction 0.7-1.0 mm). 3ml of these fragments are placed in a calcination oven in which 14catalysts can be calcined in parallel in separate vessels (shared gassupply to all calcination tubes). This calcination unit is inserted intoa muffle furnace from Nabotherm and charged with gas. The temperature ofthe muffle furnace was first increased linearly from room temperature ata gradient of 1.5° C./min to 275° C. under an air current of 400l(S.T.P.)/h and held there for 2 h. The gas supply was then switchedfrom air to nitrogen (400 l(S.T.P.)/h) and the system was likewiseheated to 600° C. linearly at a gradient of 1.5° C./min. At thistemperature the catalysts were held for 3 h before the furnace, leftalone, cooled to room temperature. The resultant catalyst was then againcomminuted and the particle fraction of 0.4-0.7 mm was separated off forthe catalytic tests.

In this way the following catalysts were produced within one day. Thetime required per sample without tableting and calcination wasapproximately 45 min.

1. Mo₁V_(0.4)Te_(0.2)Nb_(0.06)O_(x).

2. Mo₁V_(0.4)Te_(0.2)Nb_(0.20)O_(x).

3. MO₁V_(0.4)Te_(0.1)Nb_(0.12)O_(x).

4. Mo₁V_(0.4)Te_(0.3)Nb_(0.12)O_(x).

5. Mo₁V_(0.2)Te_(0.2)Nb_(0.12)O_(x).

6. Mo₁V_(0.5)Te_(0.2)Nb_(0.12)O_(x).

7. Mo₁V_(0.4)Te_(0.2)Nb_(0.12)O_(x).

8. Mo₁V_(0.4)Te_(0.2)Nb_(0.12)O_(x).

9. Mo_(1.3)V_(0.4)Te_(0.2)Nb_(0.12)O_(x).

10. Mo₁V_(0.4)Te_(0.2)Nb_(0.12)O_(x).

COMPARATIVE EXAMPLE 2

Production of a catalyst of compositionMo₁V_(0.4)Te_(0.2)Nb_(0.12)O_(x):

52.57 g of ammonium metavanadate (G.F.E., Nuremberg, 77.5% by weight ofV₂O₅, ideal composition: NH₄VO₃) and then the temperature was reduced to60° C. To this solution were then added 52.47 g of telluric acid (Fluka,99% H₆TeO₆) and 200.0 g of ammonium heptamolybdate hydrate (H. C.Starck, Goslar, 82.55% by weight of MoO₃, ideal composition:(NH₄)₆MO₇O₂₄.4H₂O), the components were dissolved and finally thetemperature of the solution was reduced to 30° C. (solution A). Inparallel, at 60° C., a solution of 62.23 g of ammonium niobium oxalate(H. C. Starck, Goslar, 20.3% by weight of Nb) was prepared in 250 g ofwater and its temperature after the dissolution operation was reduced to30° C. (solution B). At 30° C., solution B was added to solution A(approximately 4 min), whereupon, after a short time, an orange-redsuspension without precipitate formed. This suspension was dried in aspray dryer (apparatus from Niro, Tin=290° C., T_(out)=130° C.).

The resultant product was tableted in the same manner (diameter 16 mmheight=10 mm) and fragmented as described above. 70 g of the resultingfragments were heated in a rotary sphere oven (quartz glass sphere of 1liter internal capacity) under air (50 l (S.T.P.)/h) at a heating rateof 1.5° C./min to 275° C. and were kept at this temperature for 1 h. Thedry composition was then heated to 600° C. under nitrogen (50l(S.T.P.)/h) at a heating rate of 1.5° C./min and kept at thistemperature for 2 h. The cooling to room temperature was likewiseperformed under nitrogen.

The time required for producing the sample without tableting andcalcination was approximately 5 h.

The invention claimed is:
 1. A process for the sequential production ofa library of N different solids, comprising heterogeneous catalysts,wherein N, within a day of beginning production, is an integer of atleast 2, the process comprising a) producing at least two differentsprayable solutions, emulsions and/or dispersions of elements and/orelement compounds of the chemical elements present in the catalysts, b)continuously metering the at least two different solutions, emulsionsand/or dispersions in a predefined ratio into a mixing apparatus inwhich the solutions, emulsions and/or dispersions are homogeneouslymixed to form a mixture, c) continuously drying the mixture removed fromthe mixing apparatus, wherein the drying is performed by spray drying orspray-freeze drying, to produce a dried mixture, and recovering thedried mixture that is a solid, and d) changing the ratios in b) andrepeating b), c) and d) (N−1) times until N different solids areobtained; wherein the ratio in b) and d) is set and changed by changingor adapting the flow velocities of the different solutions, emulsionsand/or dispersions during the metering into the mixing apparatus and thetotal stream of the individual solutions, emulsions and/or dispersionsremains constant during the metering in the mixing apparatus and to thedrying.
 2. The process as claimed in claim 1, wherein a time periodbetween mixing the solutions, emulsions and/or dispersions and drying isa positive time period of less than 10 minutes.
 3. The process asclaimed in claim 1, wherein the different solids are produced in eachcase in amounts of from 0.1 to 500 g.
 4. The process as claimed in claim1, wherein the ratio in b) is set and changed by central computercontrol of output of pumps which in each case separately transport thedifferent solutions, emulsions and/or dispersions into the mixingapparatus.
 5. The process as claimed in claim 1, wherein the solidsobtained in d) are tested for a desired catalytic property by a processcomprising, separately introducing the individual solids into multiplereactors, and subsequently testing each solid for the desired catalyticproperty.
 6. The process of claim 1, wherein N is at least
 9. 7. Theprocess of claim 1, wherein N is at least
 45. 8. The process of claim 1,wherein N is at least
 90. 9. The process of claim 1, wherein N rangesfrom at least 2 to 5,000.
 10. The process of claim 1, wherein N rangesfrom at least 2 to 50,000.
 11. The process of claim 1, wherein thedifferent solids are produced in each case in amounts of from 1 to 100g.
 12. The process of claim 1, wherein the at least two differentsprayable solutions, emulsions, and/or dispersions each have a dissolvedsolids content and/or a solids content of 0.5 to 50% by weight, based onthe total weight of the solution, emulsion and/or dispersion.
 13. Theprocess of claim 1, wherein the at least two different sprayablesolutions, emulsions, and/or dispersions each have a dissolved solidscontent and/or a solids content of 1 to 30% by weight, based on thetotal weight of the solution, emulsion and/or dispersion.
 14. Theprocess of claim 1, wherein each sprayable solution, emulsion and/ordispersion comprises a unique element compound.
 15. The process of claim14, wherein each unique element compound is differently selected fromone of ammonium heptamolybdate, ammonium metavanadate, ammoniumparatungstate, iron (II) nitrate, iron (III) nitrate, silver nitrate,bismuth nitrate, iron sulfate, titanium oxysulfate, niobium oxalate,antimony titrate, or niobium tartrate.
 16. The process of claim 14,wherein each unique element compound comprises a unique catalyticallyactive metal.
 17. The process of claim 16, wherein each uniquecatalytically active metal is, individually, selected from subgroup Vand/or subgroup VI of the Periodic Table of the Elements.
 18. Theprocess of claim 16, wherein each unique catalytically active metal isselected from the platinum group of the Periodic Table of the Elements.19. The process of claim 1, wherein each sprayable solution, emulsionand/or dispersion comprises a unique element.
 20. The process of claim19, wherein each unique element is a metal and/or transition metal.